The objectives of this component are to utilize and extend the tools of genetic analysis to the understanding of genes which contribute significantly to human cardiovascular pathology. During the previous granting period, we successfully applied positional cloning strategies to isolate the gene for myotonic dystrophy, a multisystem disorder which includes cardiac conduction defects and sudden cardiac arrest as one of its cardinal features. This project has led to the understanding of a previously unanticipated mechanism for genetic mutation in man, the expansion of an unstable trinucleotide repeat sequence located ina the 3' untranslated region of the DMPK gene which is expressed at high levels in the heart. Our experimental plan is directed towards an understanding of the pathway which leads from gene to pathology in this disorder. We will attempt to develop direct assays for the pathological effects of trinucleotide repeat sequence expansion in cell cultures derived from DM patients and myocytes (peripheral and cardiac) derived from experimental animals into which mutant forms of the DMPK gene have been introduced. We will utilize transgenic mice to develop model systems to understand the basis for and factors which influence trinucleotide repeat sequence expansion in the DMPK gene. We will follow the fate of transcripts which contain expanded trinucleotide repeat sequences to identify potential targets of gene action. Gene targeting of the DMPK gene has led to the development of mouse strains in which animals which have lost DMPK function develop a late onset multisystem degenerative disorder. We will characterize the cardiac phenotype of the DMPK knockout mice and attempt to relate loss of kinase function to cardiac pathology. We will characterize the protein kinase functions of the DMPK gene, attempt to identify its substrate and determine how failure of the DMPK kinase to function leads to downstream cellular effects. Complementing our studies on the DMPK gene, we will continue our program of gene isolation, completing previously initiated collaborative studies directed towards the identification of the autosomal dominant genes for Romano-Ward long QT syndrome and the defect in cholesterol metabolism in Schnyder's corneal dystrophy. We will apply the repeat expansion technique developed during the previous granting period to assess the potential role of unstable repeat sequence expansion in the genetics of cardiovascular disorders such as primary pulmonary hypertension. We will complete the development of a high throughput genotyping strategy to make possible the accurate mapping and identification of genes affecting cardiac development and hypertension in the mouse. We then plan utilize this approach to identify others genes of significance to cardiovascular pathology in mouse model systems, as well as extending this methodology to human studies utilizing sib pair or other designs with appropriate power to identify genes significant to atherosclerosis, hypertension as well as other conditions in human cardiovascular disease.